Ecosystem vulnerability of China under B2 climate scenario in the 21st century

This paper applies climate change scenarios in China based on the SRES assumptions with the help of RCMs projections by PRECIS （providing regional climates for impacts studies） system introduced to China from.the Hadley Centre for Climate Prediction and Research at a high-resolution （50 kmx50 km） over China. This research focuses on B2 scenario of SRES. A biogeochemical model ＂Atmosphere Vegetation Integrated Model （AVIM2）＂ was applied to simulating ecosystem status in the 21st century. Then vulnerability of ecosystems was assessed based on a set of index of mainly net primary production （NPP） of vegetation. Results show that climate change would affect ecosystem of China severely and there would be a worse trend with the lapse of time. The regions where having vulnerable ecological background would have heavier impacts while some regions with better ecological background would also receive serious impacts. Extreme climate even would bring about worse impact on the ecosystems. Open shrub and desert steppe would be the two most affected types. When the extreme events happen, vulnerable ecosystem would extend to part of defoliate broad-leaved forest, woody grassland and evergreen conifer forest. Climate change would not always be negative. It could be of some benefit to cold region during the near-term. However, in view of mid-term to long-term negative impact on ecosystem vulnerability would be enormously.     

Determining factors in potential evapotranspiration changes over China in the period 1971–2008

Potential evapotranspiration (ET_o) is important to hydrological cycling and the global energy balance. Based on a modified FAO56-Penman-Monteith model, ET_o was simulated for 603 meteorological stations across China in the period 1971–2008. Spatial distribution and temporal change of ET_o were characterized, and the determining factors in ET_o were revealed by sensitivity analysis. Results show obvious regional differences in annual average ET_o and its determining factor. In general, annual average ET_o decreased in the period 1971–2008, but increased since the 1990s. Wind speed and sunshine duration were determining factors in the annual ET_o trend, with smaller contributions from relative humidity and temperature. Declining wind speed was the determining factor in decreasing annual ET_o in northern temperate regions and the Tibetan Plateau. The spatial extent of wind speed influence contracted to northwest China in summer, and expanded to the whole country in autumn. Decreasing sunshine duration was the determining factor in decreasing annual ET_o in subtropical and tropical regions, especially in summer, with a larger spatial influence mainly to the southeast of the farming-pastoral region. ET_o change has distinct impacts on earth surface ecosystems and environment depending on different determining factors.     

The application of large volume airgun sources to the onshore-offshore seismic surveys： implication of the experimental results in northern South China Sea

Onshore-offshore seismic experiments were carried out for the first time in northern South China Sea using large volume airgun sources at sea and seismic stations on land. The experimental results indicate that seismic signals from the new airgun array of R/V Shiyan 2 can be detected as far as 255 km. The signal effective area reaches nearly 50000 km2, which covers Hong Kong and Pearl River Delta. Compared with the old airgun array, the signal amplitude, propagation distance and effective area of the new airgun array have been increased notably, which demonstrates that the upgrade of the airgun source was successful. Comparisons with previous experimental results in other regions show that the shooting effect of the new airgun array is similar to those best airgun sources in the world. Especially, it is a new breakthrough in using the permanent seismic stations onshore to record long distance airgun signals offshore, which has great significance to the realization of the "seismic radar" concept and the 3D seismic surveys of crustal structure in coastal areas.